Low profile intravascular ultrasound catheter

ABSTRACT

The present invention provides low profile intravascular ultrasound catheters adapted to access sites within the patient&#39;s body through narrow blood vessels, e.g., the radial artery. In an embodiment, a low profile catheter comprises an catheter sheath, a short guidewire receiver attached to the distal end of the catheter sheath, and a telescope assembly at the proximal end. The catheter sheath comprises a main portion and a tapered portion for increased flexibility toward the distal end of the catheter. In one embodiment, a rotatable and translatable imaging core is received within the catheter sheath for ultrasound imaging. A short guidewire receiver is used to allow the imaging core to be advanced farther distally with respect to the distal end of the catheter. In an embodiment, the catheter sheath extends through a portion of the telescope assembly to provide enhanced support of the imaging core within the telescope assembly.

FIELD OF THE INVENTION

The present invention relates to catheters, and more particularly to lowprofile intravascular catheters.

BACKGROUND INFORMATION

Intravascular ultrasound imaging systems (IVUS) are used to obtainultrasound images inside a patient's body. An IVUS system typicallyincludes an ultrasound catheter having a flexible catheter sheathadapted for insertion into the vascular system of the patient. To obtainultrasound images, the catheter comprises an imaging core receivedwithin a lumen of the catheter sheath. The imaging core comprises anultrasound transducer connected to the distal end of a flexible drivecable that extends to the proximal end of the catheter through thecatheter lumen. The drive cable is used to rotate and longitudinallytranslate the transducer within the catheter lumen to obtain images atdifferent positions within the patient's body.

An IVUS catheter is commonly advanced through a guide catheter to adesired site within the patient's body. A problem with existingcatheters is that they are adapted for use with guide catheters that are6 French or greater in diameter. As a result, these catheters can not beused to access desired sites within the patient's body through narrowerblood vessels, e.g., the radial artery, without risk of vessel spasm.

Therefore, there is a need for a low profile intravascular catheter thatcan be used with guide catheters that are 5 French or smaller indiameter. Such a catheter would allow easier access to sites within thepatient' s body through the radial artery.

SUMMARY OF THE INVENTION

The present invention provides low profile intravascular ultrasoundcatheters adapted to access sites within the patient's body throughnarrow blood vessels, e.g., the radial artery.

In a preferred embodiment, a low profile intravascular catheter isadapted to navigate through a guide catheter that is 5 French(approximately 0.066 inch) or smaller in diameter. This allows thecatheter to more easily access sites within the vascular system (e.g.,coronary vessel) through the radial artery.

In an exemplary embodiment, a low profile catheter comprises anelongated catheter sheath, a short guidewire receiver attached to thedistal end of the catheter sheath, and a telescope assembly at theproximal end of the catheter sheath. The catheter sheath comprises amain portion and a tapered portion located distally to the main portion.The tapered portion has an outer diameter and wall thickness thatgradually decreases along the length of the tapered portion toward thedistal end of the catheter. The tapered portion provides increasedflexibility toward the distal end of the catheter enhancing thecatheter's ability to navigate the tortuous path of a blood vessel andfacilitating lesion crossibility. The tapered portion also provides agradual increase in stiffness toward the main portion of the cathetersheath for increased pushability of the catheter through the bloodvessel.

In one embodiment, a rotatable and translatable imaging core is receivedwithin a lumen of the catheter sheath for obtaining ultrasound images atdifferent positions within the patient's body. In an embodiment, theimaging core comprises an ultrasound transducer with a rectangular faceto maximize the ultrasound emitting surface area of the transducer withrespect to the catheter size. In another embodiment, the length of theguidewire receiver attached to the distal end of the sheath is keptshort to allow the imaging core to be advanced farther distally withrespect to the distal end of the catheter.

In one embodiment, the catheter comprises a telescope assembly at theproximal end of the catheter sheath. The telescope comprises a femaletelescoping tube and a male telescoping tube adapted to slid within thefemale telescoping tube to retract and extend the telescope assembly. Inan embodiment, the catheter sheath extends through the femaletelescoping tube to provide enhanced support for the imaging core withinthe female telescoping tube.

Other systems, methods, features and advantages of the invention will beor will become apparent to one with skill in the art upon examination ofthe following figures and detailed description. It is intended that allsuch additional systems, methods, features and advantages be includedwithin this description, be within the scope of the invention, and beprotected by the accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES

In order to better appreciate how the above-recited and other advantagesand objects of the present inventions are objected, a more particulardescription of the invention briefly described above will be rendered byreference to specific embodiments thereof, which are illustrated in theaccompanying drawings. It should be noted that the components in thefigures are not necessarily to scale, emphasis instead being placed uponillustrating the principles of the invention. Moreover, in the figures,like reference numerals designate corresponding parts throughout thedifferent views. However, like parts do not always have like referencenumerals. Moreover, all illustrations are intended to convey concepts,where relative sizes, shapes and other detailed, attributes may beillustrated schematically rather than literally or precisely.

FIG. 1 shows a low profile catheter according to an example embodimentof the present invention.

FIG. 2 shows a close up view of the distal portion of the catheteraccording to an example embodiment of the present invention.

FIG. 3 shows a cross-sectional view of the distal portion of thecatheter including an imaging core according to an example embodiment ofthe present invention.

FIG. 4 shows a close up view of the distal portion of the imaging coreaccording to an example embodiment of the present invention.

FIG. 5 shows a top view of a transducer housing according to an exampleembodiment of the present invention.

FIG. 6 shows a cross-sectional view of the distal portion of the imagingcore according to an example embodiment of the invention.

FIGS. 7 and 8 show exploded views of a telescope assembly according toan example embodiment of the present invention.

FIGS. 9 and 10 show cross-sectional views of the telescope assemblyaccording to an example embodiment of the present invention.

FIG. 11 shows the catheter coupled to a catheter drive system accordingto an example embodiment of the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a low profile intravascular ultrasound catheter 10according to an embodiment of the present invention. The low profileultrasound catheter 10 is adapted access sites within the patient's bodythrough narrow blood vessels, e.g., the radial artery. In the preferredembodiment, the sheath 20 of the catheter 10 is adapted to navigatethrough a guide catheter that is 5 French (approximately 0.066 inch) orsmaller in diameter. Thus, the low profile catheter 10 is preferably 5French compliant. This allows the catheter 10 to more easily accesssites within the vascular system (e.g., coronary vessel) through theradial artery. Access through the radial artery provides for greaterpatient comfort during a follow up procedure, in which an area of thevascular system that has undergone an operation is examined postoperation.

The catheter 10 comprises an elongated catheter sheath 20 having adistal portion 27, a tapered portion 25, and a main portion 23. Thecatheter sheath 20 may be coated with a lubricious coating to facilitatemovement of the sheath 20. The tapered portion 25 is located distallyfrom the main portion 23 of the catheter sheath 20 to provide increasedflexibility of the catheter sheath 10 toward the distal end. Thecatheter 10 also includes a short guidewire receiver 50 attached to thedistal end of the catheter sheath 20 for receiving a guidewire (notshown). The guidewire receiver comprise a guidewire rail with a lumenadapted to receive the guidewire. Further, the catheter 10 includes atelescope assembly 30 at its proximal end for translating an imagingcore (shown in FIG. 3) longitudinally within the catheter sheath 20.

FIGS. 2 and 3 show the distal portion of the catheter 10. As shown inFIG. 3, the catheter sheath 20 has a lumen for receiving an imaging core35. The imaging core 35 is able to rotate and translate longitudinallywithin the lumen of the catheter sheath 20 for imaging the interior ofthe patient. The imaging core 35 is described in greater detail below.

The main portion 23 of the catheter sheath 20 preferably has a wallthickness that is thick enough to provide pushability for the catheter10, where pushability is the ability of the catheter to transmit apushing force applied to its proximal end so that the catheter can bepushed through a blood vessel from the proximal end. In an embodiment,the main portion of the catheter sheath has an outer diameter ofapproximately 0.039 inches and wall thickness of approximately 0.006inches, and an effective length of approximately 135 cm. The outerdiameter is preferably less than 0.045 inches for 5 French compliance.

The tapered portion 25 of the catheter sheath 20 has an outer diameterand wall thickness that gradually decreases along the length of thetapered portion 25 in the direction from the main portion 23 to thedistal portion 27 of the sheath 20. In an exemplary embodiment, thetapered portion 25 has an outer diameter of 0.039 inches and a wallthickness of 0.006 inches at its proximal end that tapers down to anouter diameter of 0.033″ inches and a wall thickness of 0.003 inches atits distal end. The tapered portion 25 has a length of between 10 cm and20 cm. The tapered portion 25 increases the flexibility of the catheter10 toward the distal end, enhancing the catheter's 10 ability tonavigate the tortuous path of a blood vessel. The distal portion 27 ofthe catheter sheath has an outer diameter of 0.033 inches, a wallthickness of 0.003 inches, and a length of about 2.5 cm.

The sheath may be made of a variety of polymeric materials, such aspolytetrafluoroethylene (PTFE), polyethylene, PEEK, PEBAX or the like.In one embodiment, the main portion 23, tapered portion 25, an distalportion 27 of the catheter sheath are separate polymer tubes that arebonded together to form the catheter sheath 20. The main portion 23 andtapered portion 25 may be bonded together. For example, the two portionsmay be bonded together by an adhesive and then heated to fuse the twoportions together (e.g., in a reflow process). The tapered portion 25and distal portion 27 may be bonded in a similar manner. The taperedportion 25 may be fabricated using an extrusion process to graduallydecrease the outer diameter and wall thickness of the tapered portion 25along its length.

FIGS. 2 and 3 show the short guidewire receiver 50 attached to thedistal end of the catheter sheath 20. The guidewire receiver 50preferably comprises an elastomeric material with a lubricious liner.For example, the guidewire receiver 50 may be made of ethylene vinylacetate (EVA) with a Teflon liner. During operation, a guidewire (notshown) is advanced through a blood vessel to a desired site. Theproximal end of the guidewire is then threaded through the guidewirereceiver 50 to guide the catheter 10 to the desired site. The length ofthe guidewire receiver 50 is kept short to provide greater distal accessfor the imaging core 35 within the catheter sheath 20. Keeping thelength of the guidewire receiver 50 short allows the imaging core 35 tobe advanced farther distally. In one embodiment, the guidewire receiver50 has a length of 13 millimeters. Preferably, the receiver 50 is lessthan 20 millimeters in length. In FIG. 3 the unit of measurement insidethe brackets is millimeters.

FIG. 3 shows a close up cross-sectional view of the short guidewirereceiver 50. The guidewire receiver 50 has a lumen 60, a distal openingfor receiving the guidewire, and proximal opening for the guidewire toexit the guidewire receiver 50. In an exemplary embodiment, the lumen 60has a diameter of 0.016 inches. The distal tip 53 of the guidewirereceiver 50 has a beveled shape or chamfer to enhance the crossibilityof the catheter 10, where crossibility is the ability of the catheter 10to move across the surface of a narrow passage. The distal tip 53 mayhave other shapes to enhance crossibility, e.g., curved surface. Theguidewire receiver 50 may also include a radio opaque marker 65 forproviding fluoroscopic guidance of the catheter 10. Preferably, theguidewire receiver 50 has an outer diameter of less than 0.045 inches.

In the exemplary embodiment shown in FIGS. 2 and 3, the guidewirereceiver 50 is attached to the catheter sheath 20 at an angle to thelongitudinal axis of the catheter sheath 20. The angles may be 6degrees, preferably less than 10 degrees. The proximal portion 55 of theguidewire receiver 50 attached to the catheter sheath 20 tapers downwardand the portion 57 of the catheter sheath 20 attached to the guidewirereceiver 50 tapers upward. This tapering of the guidewire receiver 50and the catheter sheath 20 maintains the low profile of the catheter 10throughout the region 58 where the guidewire receiver 50 attaches to thecatheter sheath 20. The proximal portion 55 of the guidewire receiver 50and the portion 57 of the catheter sheath 20 may be bonded together,e.g., by heat bonding. Heat applied during the bonding process may beused to reshape the portion 57 of the catheter sheath 20 attached to theguidewire receiver 50 from a generally cylindrical shape to the shapeshown in FIGS. 2 and 3. This may be done, e.g., by applying heat tosoften the catheter sheath 20 and using a clamp to reshape the softenedsheath into the desired shape.

FIGS. 4-6 show an exemplary imaging core 35 that can be received in thecatheter sheath 20 for ultrasound imaging. Preferably, the portion ofthe sheath 20 from which the imaging core 35 images is acousticallytransparent to allow for the transmission of ultrasound waves throughthe sheath 20. The imaging core 35 comprises an ultrasound transducer105, e.g., a piezoelectric crystal (PZT), connected to the distal end ofa drive cable 110, which extends through the lumen of the cathetersheath 20. The drive cable 110 is used to rotate and translate thetransducer 105 within the catheter sheath 20. The drive cable 110preferably possesses a high torsional stiffness so that the drive cable110 can transmit torque from a drive motor (not shown) to the transducerto rotate the transducer 105. The drive cable 110 also possesses a lowbending stiffness allowing the drive to bend along a tortuous path of ablood vessel. For example, the drive cable 100 may comprise twocounterwound coils.

FIG. 6 show a cross-sectional view of the distal portion of the imagingcore 35. The imaging core 35 comprises a transducer housing 115 attachedto the distal end of the drive cable 20. The transducer housing 115 maybe made of steel, and has a curved tip 120 to facilitate forwardmovement of the imaging core 35 in the catheter sheath 20 lumen. Thetransducer housing 115 also has a space for receiving the transducer,and an attachment portion 125 for attaching the transducer housing 115to the drive cable 110. In this embodiment, the attachment portion 125has a generally cylindrical shape and fits around a distal portion 130of the drive cable 125 and is bonded to the drive cable 110 by solder.

The imaging core 35 further comprises a transducer assembly housedwithin the transducer housing 115. The transducer assembly comprises thetransducer 105, e.g., PZT, a matching layer 135 on top of the transducer105 and a backing layer 140 on the bottom of the transducer 105. Thematching layer 135 provides acoustic matching between the transducer 105and the surrounding fluid. The backing layer 140 is made of anacoustically absorbent material to direct emissions of ultrasound wavesfrom the top of the transducer 105. In this exemplary embodiment, thetransducer 105 has a rectangular face to maximize the ultrasoundemitting surface area of the transducer 105 relative to the size of thehousing 115. This improves both the transducer 105 output andsensitivity while maintaining a low profile. The transducer 105 may betilted at a slight angle so that ultrasound waves are emitted at aslight angle relative to the perpendicular direction. This is done sothat ultrasound waves that are reflected off the catheter sheath 20 arenot directed back to the transducer 105.

The imaging core 35 further comprises a twisted pair wire 145 runningthrough a central lumen in the drive cable 110. The twisted pair wire145 provides electrical communication between the transducer 105 and theproximal end of the drive cable 110, which is electrically coupled toultrasound electronics (not shown), e.g., by an inductive coupler, sliprings or the like. The twisted pair wire 145 comprises a first wire 150electrically coupled to the top of the transducer 105 through thematching layer 135 and second wire 155 electrically coupled to thebottom of the transducer 105 through a conductive epoxy 160 and theconductive backing layer 140. The first wire 150 is attached to thematching layer 135 by a solder bump 165 or other conductive adhesive.The second wire 155 is encased in the conductive epoxy 160 which forms aconduction path to the conductive backing layer 140. The first wire 150and the transducer 105 are encased in a non-conductive epoxy, whichprevents the top and bottom terminals of the transducer 105 fromshorting out. The conductive epoxy 160 electrically couples the secondwire to the metal transducer housing 115, which acts as a electricalground. The conductive and non-conductive epoxy 160, 170 help hold thetransducer assembly in place in the transducer housing 115. As shown inFIG. 5, the transducer assembly is fitted between two side walls 117 ofthe transducer housing 115.

Referring to FIGS. 7-10, the telescope assembly 30 comprises a maletelescoping tube 220, a female telescoping tube 215, and a hub 225attached to distal end of the female telescoping tube 220. The maletelescoping tube 220 is adapted to be slidably received within thefemale telescoping tube 215. The hub 225 has a strain relief 230 in theform of a helical section that provides a gradual decrease in stiffnesstoward the distal end of the strain relief 230.

The telescope assembly 35 further comprises a telescope housing 235 thatslidably couples the male telescoping tube 220 to the female telescopingtube 215. Referring to FIGS. 9 and 10, the telescope housing 235comprises a lumen into which a proximal portion of the femaletelescoping tube 215 is inserted. The proximal portion of the femaletelescoping tube 215 is bonded to the telescope housing 235, e.g., usinga UV activated adhesive. The male telescoping tube 210 passes throughthe lumen of the telescope housing 235 and comprises a flared portion240 at its distal end. The mate telescoping tube 220 is adapted to slidethrough the lumen of the telescope housing 235 and into the femaletelescoping tube 215. The telescope housing 235 includes a stop member243 that engages the flared portion 240 of the male telescoping tube 220when the telescope assembly is fully extended to prevent the maletelescoping tube from being pulled out of the telescope housing 235. Thetelescope housing 235 further comprises an o-ring 245 and a ring seal250 that provide a sliding seal between the male telescoping tube 220and the housing 235. The o-ring 245 is seated in the lumen between thestop member 243 and the seal 250. The outer surface of the ring seal 250is bonded to the lumen by an adhesive 253 shown in FIG. 8. The o-ring245 may be made with an elastomeric material such as silicon or rubber.

The proximal portion of the catheter sheath 20 extends through the hub225 and into the female telescoping tube 215 as shown in FIGS. 9 and 10.In one embodiment, the proximal portion of the catheter sheath 20extends the entire length of the female telescoping tubing 215 and intoa distal portion of the male telescoping tube 220. The male telescopingtubing 220 is dimensioned to slide over the catheter sheath 20. Thus,the male telescoping tube 220 slides between the female telescoping tube215 and the catheter sheath 20 to retract and extend the telescopeassembly 30. The outer surface of the catheter sheath 20 is preferablybonded to the hub 225, e.g., using epoxy. In one embodiment, the imagingcore 35 is placed in the sheath 20 before the sheath 20 is bonded to thehub 225. In this embodiment, the sheath 20 is moved to a desiredposition relative to the imaging core 35, at which point the sheath 20is bonded to the hub 225. This method of assembly facilitates accuratepositioning of the sheath 20 relative to the imaging core 35.

The portion of the catheter sheath 20 extending into the femaletelescoping tube 215 provides enhanced support for the drive cable 110of the imaging core 35 within the female telescoping tube 215. Withoutthe portion of the catheter sheath 20 extending into the female tube225, the drive cable 110 would lie unsupported in the female telescopingtube 225 when the telescope assembly is in the fully extended position.The enhanced support provided by the portion of the catheter sheath 20within the female telescoping tube 215 prevents wind-up and kinking ofthe drive cable 110.

The telescope housing 235 includes a notch 255 around the outercircumference of the housing 235. The notch 255 snaps onto a clip of acatheter drive system, an example of which is shown in diagram form inFIG. 11. The exemplary catheter drive system comprises a sled 280, adrive unit 275 that moves longitudinally along the sled 280, and a clip283 at the distal end of sled 280. The clip 283 is adapted to engage thenotch 255 of the telescope housing 235 to anchor the telescope housing235 to the sled 280. Because the female telescoping tube 215 is attachedto the telescope housing 235 and the catheter sheath 20 and the femaletube 215 are both attached to the hub 225, anchoring the telescopehousing 235 to the sled 280 also anchors the female tube 215 and sheath20 to the sled 280. The male telescoping tube 220 and the drive cable110 of the imaging core 35 are mechanically coupled to the drive unit275, e.g., by a hub connector (not shown). The drive unit 275 is used totranslate the male telescoping tube 220 and the imaging core 35longitudinally relative to the catheter sheath 20, which is anchored tothe sled 280. The drive unit may 275 include a translator drive motor(not shown) for translating the drive unit longitudinally, and a rotarydrive motor (not shown) for rotating the imaging core within thecatheter body. As shown in FIG. 11, the catheter system may include aflush port 285 for delivering fluid into the catheter sheath lumen,e.g., during a flushing procedure. Further details of catheter drivesystems can be found, for example, in U.S. Pat. No. 6,398,755, titled“Driveable Catheter System,” issued on Jun. 4, 2002, the specificationof which is incorporated by reference.

During an operation, the catheter 10 is advanced, e.g., through theradial artery, to a desired site in the patient's vascular system. Inone embodiment, the catheter 10 is advanced through a guide catheter(not shown) to the desired site. After the catheter 10 and imaging core35 are positioned at the desired site, the catheter sheath 20 isanchored (locked) to the sled 280. Preferably the imaging core 35 ispositioned distally within the catheter sheath 20 and the telescopeassembly is in a retracted state. The short guidewire receiver 50enables the imaging core 35 to be positioned closer to the distal end ofthe catheter 10, and therefore farther into the patient's vascularsystem. After the catheter sheath 20 is locked in place, the imagingcore 35 is rotated to obtain radial cross-sectional images of the site.In addition, the male telescoping tube 220 and imaging core 30 arepulled back by the drive unit 275. This extends the telescope assemblyand moves the imaging core 35 longitudinally within the sheath 20allowing the image core 35 to obtain radial cross-section images atdifferent potions along a length of the desired site. Thesecross-sectional images can be aggregated by an ultrasound processor intoa three dimensional image.

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It will, however, be evidentthat various modifications and changes may be made thereto withoutdeparting from the broader spirit and scope of the invention. Forexample, the reader is to understand that the specific ordering andcombination of process actions described herein is merely illustrative,and the invention can be performed using different or additional processactions, or a different combination or ordering of process actions. As afurther example, each feature of one embodiment can be mixed and matchedwith other features shown in other embodiments. Additionally andobviously, features may be added or subtracted as desired. Accordingly,the invention is not to be restricted except in light of the attachedclaims and their equivalents.

1. An intravascular catheter, comprising: a catheter sheath having amain portion, a distal portion, and a tapered portion located betweenthe main portion and the distal portion, wherein the tapered portion hasa length in a range of 10 to 20 centimeters and has a wall thicknessthat gradually decreases in a direction toward the distal portion of thecatheter sheath, the catheter sheath comprising a lumen configured andarranged for receiving an imaging core, the lumen extending to thedistal portion of the catheter sheath; a guidewire receiver attached tothe distal portion of the catheter sheath, the guidewire receivercomprising a lumen for receiving the guidewire and an opening forinsertion of a guidewire into the guidewire receiver from an exterior ofthe intravascular catheter; and a telescoping assembly attached to aproximal portion of the catheter sheath.
 2. The catheter of claim 1,wherein the tapered portion of the catheter sheath has a maximum outerdiameter of less than 0.045 inches.
 3. The catheter of claim 1, whereinthe guidewire receiver has a length of 20 millimeters or less.
 4. Thecatheter of claim 1, the guidewire receiver has an angled proximalportion attached to the distal portion of the catheter sheath.
 5. Thecatheter of claim 4, wherein the distal portion of the catheter sheathhas an angled distal region attached to, and overlapping with, theangled proximal portion of the guidewire receiver.
 6. The catheter ofclaim 5, wherein a region within which the angled proximal portion ofthe guidewire receiver attaches to the angled distal region of thedistal portion of the catheter sheath has a substantially uniform outerdiameter.
 7. The catheter of claim 1, wherein a longitudinal axis of theguidewire receiver is at an angle with respect to a longitudinal axis ofthe catheter sheath.
 8. The catheter of claim 7, wherein the angle isapproximately between 5 and 10 degrees.
 9. The catheter of claim 7,wherein the guidewire receiver has an outer diameter of 0.045 inches orless.
 10. The catheter of claim 1, further comprising an imaging corereceived within a lumen of the catheter sheath.
 11. The catheter ofclaim 1, wherein the telescope assembly comprises: a female telescopingtube; and a male telescoping tube adapted to slide within the femaletelescoping tube; wherein a proximal portion of the catheter sheathextends into the female telescoping tube, and the male telescoping tubeis adapted to slide over the proximal portion of the catheter sheath.12. The catheter of claim 11, wherein the proximal portion of thecatheter sheath extends through the female telescoping tube and into adistal portion of the male telescoping tube when the telescope assemblyis in a fully extended state.
 13. The catheter of claim 12, furthercomprising an imaging core extending through the male telescoping tubeand a lumen of the catheter sheath.
 14. The catheter of claim 11,wherein the telescope assembly further comprises a telescope hub,wherein a distal portion of the female telescoping tube is attached tothe hub, and the proximal portion of the catheter sheath extends throughthe hub into the female telescoping tube.
 15. The catheter of claim 14,wherein the proximal portion of the catheter sheath and a portion of thecatheter sheath extending distally from the hub comprise a singlecontinuous tubular piece.
 16. The catheter of claim 4, Wherein a joint,formed by overlapping the angled distal region of the catheter sheathwith the angle proximal portion of the guidewire receiver, has alongitudinal axis that is angled with respect to a longitudinal axis ofthe catheter sheath.
 17. The catheter of claim 1, wherein the distalportion of the catheter sheath comprises a distal region that is taperedand the guidewire receiver comprises a proximal portion that is tapered,wherein the distal region of the catheter sheath is bonded to theproximal portion of the guidewire receiver.
 18. The catheter of claim17, Wherein the catheter sheath comprises a longitudinal axis andwherein the guidewire receiver is attached to the catheter sheath at anon-zero angle to the longitudinal axis of the catheter sheath.
 19. Thecatheter of claim 18, wherein the non-zero angle is at least 6 degreesand less than 10 degrees.
 20. The catheter of claim 17, wherein thedistal region of the catheter sheath is tapered upward and the proximalportion of the guidewire receiver is tapered downward.